Posted
by
CowboyNealon Thursday May 03, 2007 @07:21PM
from the but-no-ragnaros dept.

mattatwork writes "According to ScienceDaily, NASA has come to the conclusion that the planet Mercury may have a molten core after all, based on high-precision planetary radar readings. You may (or may not) remember the Mariner 10 probe making 3 passes by Mercury between March 29th, 1974, September 21st 1974 and March 16, 1975."

It ain't THAT bad. I don't eat there very often myself, but that's more for the same reason I don't like to use Microsoft products: they drive the little guys out of business (well, not McD's specifically, but big chains in general). I'd rather eat at small independently owned restaurants around town just because the atmosphere is better, and the food doesn't taste exactly the same wherever you go. I also am not a hamburger fan (I eat them, but only every couple months). Overall though, the food at McDo

I have to disagree with you the food at McDonalds is disgusting, save the grilled chicken sandwich(not great but not bad), the fruit and yogurt salad(damn good actually), and the Egg McMuffin. The rest is nasty tasting processed junk and the after taste of McNuggets ech... it's like gasoline. I have to be honest with you I can't remember the last time I ate a burger there it was at least 5 years ago. So things may have changed, since then, but I'm not interested in trying.

The rest is nasty tasting processed junk and the after taste of McNuggets ech... it's like gasoline.

I think you just figured out what the secret ingredient is.

Their menu consists solely of varying proportions of salt, sugar, soy protein, various starches, chemicals and oils extracted from corn, "beef products", "chicken products", and hydrogenated oils (synthetic fat). It tastes like it too. So some random petroleum derived-hydrocarbons would probably improve the taste a bit.

well technically "molten" is a relative term. To beings on Pluto the earth would be covered with rivers of molten water. So perhaps from the perspective of hot compared to a star, then magma might be cold.

well technically "molten" is a relative term. To beings on Pluto the earth would be covered with rivers of molten water. So perhaps from the perspective of hot compared to a star, then magma might be cold.

In that case the temperature would be the relative term. The water is, of course, molten (in the sense of "made liquid by heat", which I think is the most common), so there is no relative use of the word there. Besides: Come on, cold magma? We might as well extract some of it to cool our beers once we g

I suppose the longer Mercury can hold out as an active planet, the longer will should last as one... assuming we make it that far...

I do not know much about this, but is it possible Mercury would always have a molten core just do the extremes it endures (gravity, radiation, cosmic whatever, etc). If true, then my above statement is holds no value.

I do not know much about this, but is it possible Mercury would always have a molten core just do the extremes it endures (gravity,...[snipped]

I had the same thought regarding gravity. Since Mercury's orbit is not circular, isn't it subject to the same type of tidal forces that induces Jupiter's satellite Io's molten core? Is there a planetary poohbah among us who might enlighten we curious but lazy 'dotters? Thank you in advance.

Tidal forces should have little effect on Mercury since it's already tidally locked. The same side always faces the sun. The locking occurred because Mercury was once rotating, and tidal forces mostly affect rotating planets. They stretch the planet out like an egg pointing at the sun and Mercury is probably a little egg-shaped.When the planet is rotating, the tidal force axis swings around all longitudes during the day and it's as if the sun were rolling the planet between its fingers. It gets squashed and

Don't listen to this guy. Mercury is not tidally locked with the sun, but rotates very slowly at about 3 rotations for every 2 revolutions around the sun. And even more, an ocean does not act as any sort of a buffer against gravitational forces from the sun. There's just not a significant enough amount of water even on Earth to do so.

Mercury is not tidally locked with the sun, but rotates very slowly at about 3 rotations for every 2 revolutions around the sun.

I forgot my Mercury trivia; they used to think it was locked [nature.com] before they found the 3/2 resonance. Since the resonance is stable, rotational energy is not being affected anymore. But then that means tidal forces are still heating Mercury over a 1400 hour cycle. The heat loss from friction is probably coming out of the orbital energy making the orbit unstable.

And even more, an ocean does not act as any sort of a buffer against gravitational forces from the sun. There's just not a significant enough amount of water even on Earth to do so.

OK, so the water transmits zero torque until there's how much of it then?

Most of the torque being applied to slow the earth down is transmitted at two hydrosphere/lithosphere boundaries: the one between the inner and outer core, and the one between the crust and the oceans. This is because unlike solid rock, fluids are free to slosh around horizontally. The outer core has more mass but the moment arm and surface area are both bigger for the oceanic boundary.

OK, so the water transmits zero torque until there's how much of it then?

Oh come on, you made a stupid claim. There's no "cushion" to solar torque (well perhaps a couple of minor ones). The bedrock experiences as much tidal force as before. And since it is around 8000 miles thick and about a factor of five denser than ocean, the counterforce from the slightly higher water levels isn't relevant. The other effect is that the rotation is slowed somewhat more than it would otherwise be which reduces the fre

"I suppose the longer Mercury can hold out as an active planet, the longer will should last as one... assuming we make it that far..."

This may change some of the basic assumptions we have regarding planet formation and tectonic activity. Terrestrial/rocky planets start out molten due to heat of accretion and differentiate as they cool. In a way, the Earth and now apparently Mercury are actually still forming because they are partially molten.

An example of a completely cooled-off, solidified planet would be Mars. It was generally thought that Mars is no longer tectonically active - no long molten in the middle - because it is smalle

I would imagine its proximity to the sun plays a part in it; hot objects in cooler areas cool off faster than hot objects in warmer areas, after all. It's true that mercury is considerably smaller than mars, but its proximity to the sun, and all of its heat, is considerably closer than mars is. After all, the surface temperature of Mercury is, what, 400 some degrees when facing the sun?

Even if this is true, however, intuitively speaking, it kinda doesn't seem like it would be enough to keep the core act

Tidal forces are the driving factor for maintaining a liquid core. Europa, Io, Earth, Titan, and now Mercury illustrate this. Mars is larger and closer to the sun than all these moons, but has no tidal forces.
1. Our own moon violates this rule (it should be heated by the tidal force of the earth). When all is said and done I think we'll find that the moon's core is, if not molten, certainly heated.
2. Venus has a liquid core I believe, and it has no companion, no tidal forces.
Yes, I realize these state

What? Ice and rock are both solids, yes, and you can find both on Earth, no need to go to Pluto. There are specific definitions for being liquid. There aren't any silicates that melt below 600C:http://hyperphysics.phy-astr.gsu.edu/hbase/ge ophys/meltrock.htmlBeing liquid is not subjective.

it is quite odd that mercury has a liquid metal core but a very weak magnetic field- planetary magnetic fields form when currents flow through a liquid core- the rotating core sustains the field as on earth, the sun and jupiter but mercury's is very weak- apparently it isn't rotating much

You know that Mercury is in tidal lock with the sun? so it only rotates (I think) once every 87 days or so. This slow rotation rate may explain the weakness of the field. Perhaps its high orbital eccentricity (0.2) and proximity to the sun, and the resultant tidal wrenching would explain the liquid mantle?

mercury has a 3:2 resonance orbit:rotation which could very well explain a very slow fluid core rotation and thus the weak field since eventually the core will sync with the rotation of the outside of the planet.

More than likely the magnetic field of the sun screws with Mercuries, considering the sun is many many times larger and thus has a magnetic field of far more power. Of and the fact that the Sun's magnetic field is caused by nuclear fusion...

If it were molten non-metal (e.g. silicates, or something more like magma) would it still generate a magnetic field? If it were 1% metal, 99% magma, would it generate a magnetic field 1% of what it would have with molten metal?

it is correct that a planet needs a conductive liquid rotating core to produce a magnetic field and mercury's density indicates that the core is composed of a large portion of iron and some sulfur
http://adsabs.harvard.edu/abs/2005AGUSM.P23A..01S [harvard.edu]

I'm definitely not an expert on the subject of planetary physics, however i do know that a major reason for Earth magetic field is the combination of the solid ferrous core with the molten ferrous mantle portions. With the mantle constantly moving around the core it creates a magnetic field (called the dynamo effect IIRC)

A landing mission with the ability to do chemical analysis would answer a lot of questions. The problem is the high energy cost, but I think this is the idea opportunity to try a solar sail for the cruise stage and mercury orbit insertion.

I think the landers should be lightweight vehicles with only a few experiments. The bulk constitution of the surface should tell us a lot about the core.

Why have I never heard of Rodinia, Pannotia, and other "supercontinents" that "existed prior to Pangaea"? I'd always been taught in my Geology classes that Pangaea was the ONLY supercontinent on geologic history. Is this even taught now?

Bringing Neal Adams into this makes me wonder a lot of things about what I wasn't told about.

I remember those Mariner missions very well. I remember them just as well as the last time I got laid. Better, actually, since the Mariner missions were more recent.The memories are a lot alike for me. I was like a little spacecraft, looking for my target in the darkness of the space under the blankets. My goal was huge. Literally, she was the size of Mercury. And she was hot too. Sweaty hot. Uncomfortable and slippery sweaty hot. I snuck a little camera in there and took some blurry low resolution pictures

...thinking to myself "What could possibly lie at Mercury's core". I went through a mental checklist. Cheese? No. Highly compacted fluffy bunnies? No. A sphere of pure neutronium? No. And then I got to hot molten magma and I thought "yup, it's gonna be pretty hot down there and Mercury is probably made of rock, so that sounds right." And guess what, now some scientists are saying the same thing. Amazing how far you can get just thinking in your armchair.

You're a pretty good example of how not teaching basic logic and how to avoid fallacious reasoning in school are so desperately needed. I can't imagine how you came to think the above argument (such as it is) has any meaning, but I truly pity anybody who has to rely upon your reasoning to reach any sound conclusion.